This command shows currently logged in users with time details

# who -u
root     tty1         2012-10-12 17:56  old         1960 (:0)
root     pts/0        2012-10-12 17:57 06:51        2376 (:0.0)
root     pts/1        2012-10-16 14:29 02:09        3094  (10.10.10.30)
root     pts/2        2012-10-16 17:51   .          3454 (10.10.10.30)